"Charles T. Low" wrote
I've spun couplers on I/O's - but am not sure if this is analagous.
When I did, the prop virtually just didn't turn, at any speed.

I decided to forego testing and dropped my prop off late yesterday (Monday)
to be rebuilt. The local shop sends them out on Tuesdays, so I wanted to go
ahead and get it in this week's truck so it would be back next week. I asked
about other causes while I was there and was told that a drive coupler could
do something similar, but that I would probably have noticed a hot smell
from that, which I didn't. Fortunately the forecast here is rain all week,
so I don't feel too bad about the boat being out of commission for a few
days.